Electrode for common cavity cochlear malformation

ABSTRACT

A method is described to implant a cochlear implant electrode into a cochlea having a single internal cavity defined by an outer cavity wall. An implantable electrode array is made of a resilient electrode carrier material and has an outer surface with one or more stimulation contacts for delivering the electrical stimulation signals to adjacent neural tissue. A distal end of the electrode array is attached to an insertion line made of a line material different from the electrode carrier material. The distal end of the electrode array is inserted through a single cochleostomy opening into the cochlea while an extra-cochlear end of the insertion line is held outside the cochleostomy opening. The remainder of the electrode array is inserted through the cochleostomy opening into the cochlea while continuing to hold the extra-cochlear end outside the cochlea to maneuver all of the stimulation contacts against the outer cavity wall.

This application claims priority from U.S. Provisional PatentApplication 61/890,927, filed Oct. 15, 2013, which is incorporatedherein by reference.

FIELD OF THE INVENTION

The present invention relates to medical implants, and more specificallyto an implantable electrode for use in cochlear implant systems inpatients having a malformed cochlea.

BACKGROUND ART

A normal ear transmits sounds as shown in FIG. 1 through the outer ear101 to the tympanic membrane (eardrum) 102, which moves the bones of themiddle ear 103 (malleus, incus, and stapes), which in turn vibrate theoval window and round window openings of the cochlea 104. The cochlea104 is a long narrow duct wound spirally about its axis forapproximately two and a half turns. The cochlea 104 includes an upperchannel known as the scala vestibuli and a lower channel known as thescala tympani, which are connected by the cochlear duct. The scalatympani forms an upright spiraling cone with a center called themodiolar where the spiral ganglion cells of the acoustic nerve 113reside. In response to received sounds transmitted by the middle ear103, the fluid-filled cochlea 104 functions as a transducer to generateelectric pulses that are transmitted to the cochlear nerve 113, andultimately to the brain.

Hearing is impaired when there are problems in the ability to transduceexternal sounds into meaningful action potentials along the neuralsubstrate of the cochlea. In such cases a cochlear implant is anauditory prosthesis which uses an implanted stimulation electrode tobypass the acoustic transducing mechanism of the ear and insteadstimulate auditory nerve tissue directly with small currents deliveredby multiple electrode contacts distributed along the electrode.

FIG. 1 also shows some components of a typical cochlear implant systemwhich includes an external microphone that provides an audio signalinput to an external signal processing stage 111 where various signalprocessing schemes can be implemented. The processed signal is thenconverted into a digital data format, such as a sequence of data frames,for transmission into the implant stimulator 108. Besides extracting theaudio information, the implant stimulator 108 also performs additionalsignal processing such as error correction, pulse formation, etc., andproduces a stimulation pattern (based on the extracted audioinformation) that is sent through connected wires 109 to an implantedelectrode carrier 110. Typically, this electrode carrier 110 includesmultiple electrodes on its surface that provide selective stimulation ofthe cochlea 104.

In some persons, the cochlear shape fails to develop properly andvarious malformation conditions can occur such as those shown in FIG. 2:cochlear aplasia, cochlear hypoplasia, common cavity (CC) malformation,and incomplete partitioning. Specifically in a common cavitymalformation the cochlea and the vestibule are represented by a singlechamber. This structure may have cochlear and vestibular neuralstructures, but it completely lacks inter-scala separation (no basilarmembrane), no modiolus trunk, and it appears as a single cavity. Theneural structures are believed to be present at the bony capsuledefining the outer cavity wall. The specific size of the cavity can varysignificantly and can be measured using medical imaging.

Placing an electrode inside a malformed common cavity cochlea is notstraightforward and needs utmost care to ensure that the stimulationcontacts are either touching or very close to the outer wall of thecavity. The current technique involves making two cochleostomy openingsin the outer surface of the cochlea for the electrode placement, whichis undesirably traumatic.

FIG. 3A shows one approach wherein the electrode array 302 has anextended distal end. Two cochleostomies 304 are made in the outersurface of the cochlea 300, the electrode array 302 is inserted throughone of the cochleostomies 304, and the distal tip of the electrode array302 is retrieved and pulled through the other cochleostomy 304. Thesurgeon has to manipulate the electrode array 302 to attempt to placethe stimulation contacts 303 against the outer wall 301 of the cavity,after which the final position of the electrode array 302 is fixed andthe distal extension may be removed.

FIG. 3B shows another approach for electrode implantation in a commoncavity, again requiring two cochleostomies 304 in the outer surface ofthe cochlea 300. Two separate electrode arrays 302 are used, one througheach cochleostomy 304, and again considerable surgical skill is neededto manipulate the electrode arrays 302 to place their stimulationcontacts 303 adjacent to the outer wall 301 of the cavity. Bothtechniques are highly traumatic in requiring two cochleostomies and bothrequire considerable surgical skill to be effective.

SUMMARY OF THE INVENTION

Embodiments of the present invention are directed to a method ofimplanting a cochlear implant electrode into a cochlea having a singleinternal cavity defined by an outer cavity wall (e.g., a malformedcommon cavity cochlea). An implantable electrode array is made of aresilient electrode carrier material and has an outer surface with oneor more stimulation contacts for delivering the electrical stimulationsignals to adjacent neural tissue. A distal end of the electrode arrayis attached to an insertion line made of a line material different fromthe electrode carrier material. The distal end of the electrode array isinserted through a single cochleostomy opening into the cochlea while anextra-cochlear end of the insertion line is held outside thecochleostomy opening. The remainder of the electrode array is insertedthrough the cochleostomy opening into the cochlea while continuing tohold the extra-cochlear end outside the cochlea to maneuver all of thestimulation contacts against the outer cavity wall.

The insertion line may be configured to be cut after feeding theelectrode array into the cochlea so that no part of the insertion lineremains within the cochleostomy opening. The electrode array may be fedthrough the cochleostomy opening until the distal end of the electrodearray contacts the outer cavity wall opposite the cochleostomy opening.Then after the distal end of the electrode array contacts the outercavity wall, the insertion line may be retracted back through thecochleostomy opening while continuing to feed the electrode arraythrough the cochleostomy opening until the distal end of the electrodearray reaches the cochleostomy opening. The distal end of the electrodearray may include an attachment ring to which the insertion line isattached. The line material may be a medical grade suture material.

Embodiments of the present invention also include a correspondingimplantable electrode. An extra-cochlear electrode lead contains signalwires for conducting electrical stimulation signals. An intra-cochlearelectrode array is configured to be inserted into the cochlea through asingle cochleostomy opening and is made of a resilient carrier materialhaving an outer surface with one or more stimulation contacts fordelivering the electrical stimulation signals to adjacent neural tissue.An insertion line is attached to a distal end of the electrode array andmade of a line material different from the electrode carrier material.The insertion line is configured to have an extra-cochlear end extendingoutside the cochleostomy opening during surgical insertion of theelectrode array into the cochlea.

In specific embodiments, the insertion line may be configured to be cutafter feeding the electrode array into the cochlea so that no part ofthe insertion line remains within the cochleostomy opening. The distalend of the electrode array may include an attachment ring to which theinsertion line is attached. The line material may be a medical gradesuture material. Embodiments of the present invention also include acomplete cochlear implant system having an electrode array according toany of the above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows elements of a human ear having a typical cochlear implantsystem.

FIG. 2 illustrates various cochlear malformation shapes.

FIG. 3 A-B show conventional electrode insertion into a common cavitycochlea using two cochleostomies.

FIG. 4 A-B show a common cavity electrode having an insertion lineaccording to an embodiment of the present invention.

FIG. 5 A-D shows insertion of a common cavity electrode into a malformedcommon cavity cochlea.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Various embodiments of the present invention are directed to animplantable electrode for a common cavity cochlea having an insertionline at a distal end of the electrode array that is suitable forinsertion into a malformed common cavity cochlea through a singlecochleostomy opening. Because the electrode is configured for insertionthrough a single cochleostomy opening rather than requiring twocochleostomies as in existing conventional arrangements, the amount oftrauma to the cochlea is reduced and an easier surgical insertionprocess can be used. And, the insertion line approach is suitable forusing a conventional cochlear implant electrode without significantstructural alteration or without special fabrication specifically for acommon cavity cochlea.

FIG. 4 A-B show an implantable common cavity electrode 400 according toone specific embodiment of the present invention. An extra-cochlearelectrode lead (not shown) contains signal wires for conductingelectrical stimulation signals to an intra-cochlear electrode array 401made of a resilient carrier material (e.g., medical grade silicone). Theouter surface of the electrode array 401 has one or more stimulationcontacts 402 for delivering the electrical stimulation signals toadjacent neural tissue in the outer cavity wall of a malformed commoncavity cochlea. The electrode array 401 is configured to be insertedinto the cochlea through a single cochleostomy opening, thereby creatingfar less trauma and using a far simpler surgical technique.

An insertion line 403 is attached to a distal end of the electrode array401 for example, by fixation to an attachment ring 404. The insertionline 403 is made of a line material different from the electrode carriermaterial; for example, medical grade surgical suture material. Theinsertion line 403 is long enough to have an extra-cochlear end thatextends outside the cochleostomy opening during surgical insertion ofthe electrode array 401 into the cochlea, which is therefore well-suitedto be fixedly held by the surgeon during the insertion process.

FIG. 5 A shows a malformed cochlea having a single internal cavity 500defined by an outer cavity wall (e.g., a malformed common cavitycochlea) having a single cochleostomy opening 501 for insertion of suchan electrode array. The distal end of the electrode array 401 initiallyis inserted through the cochleostomy opening 501 into the internalcavity 500 of the cochlea while an extra-cochlear end of the insertionline 403 is securely held outside the cochleostomy opening 501. Theelectrode array 401 is fed through the cochleostomy opening 401 untilthe distal end of the electrode array 401 contacts the outer cavity wallof the internal cavity 500 opposite the cochleostomy opening 501, asshown in FIG. 5B. Then after the distal end of the electrode array 401contacts the outer cavity wall, the insertion line 403 is retracted backthrough the cochleostomy opening 501 while continuing to feed theelectrode array 401 through the cochleostomy opening 501 and whilecontinuing to hold the extra-cochlear end of the insertion line 403outside the cochlea. As the distal end of the electrode array 401reaches the cochleostomy opening 501, as shown in FIG. 5D, the surgeonmaneuvers all of the stimulation contacts 402 against the outer cavitywall of the internal cavity 500.

The specific lengths of the electrode array 401 and/or the insertionline 403 may differ in specific embodiments in order to accommodatedifferent size internal cavities 500. And the insertion line 403 may beconfigured to be cut after fully feeding the electrode array 401 intothe internal cavity 500 of the cochlea so that no part of the insertionline 403 remains within the cochleostomy opening 501 to avoid bacterialinfection.

Although various exemplary embodiments of the invention have beendisclosed, it should be apparent to those skilled in the art thatvarious changes and modifications can be made which will achieve some ofthe advantages of the invention without departing from the true scope ofthe invention.

What is claimed is:
 1. A method of implanting a cochlear implant electrode in a cochlea having a single internal cavity defined by an outer cavity wall, the method comprising: inserting through a single cochleostomy opening a distal end of an implantable electrode array made of a resilient electrode carrier material and having an outer surface with one or more stimulation contacts for delivering electrical stimulation signals to adjacent neural tissue; wherein the distal end is attached to an insertion line made of a line material different from the electrode carrier material and configured to have an extra-cochlear end extending outside the cochleostomy opening during the inserting; continuing to feed the electrode array through the cochleostomy opening into the cochlea while holding the extra-cochlear end outside the cochlea, until the distal end of the electrode array contacts the outer cavity wall opposite the cochleostomy opening, to maneuver all of the stimulation contacts against the outer cavity wall; and after the distal end of the electrode array contacts the outer cavity wall, retracting the insertion line back through the cochleostomy opening while continuing to feed the electrode array through the cochleostomy opening into the cochlea until the distal end of the electrode array reaches the cochleostomy opening.
 2. The method according to claim 1, further comprising: cutting the insertion line after feeding the electrode array into the cochlea so that no part of the insertion line remains within the cochleostomy opening.
 3. The method according to claim 1, wherein the distal end of the electrode array includes an attachment ring to which the insertion line is attached.
 4. The method according to claim 1, wherein the line material is a medical grade suture material.
 5. The method according to claim 1, wherein the cochlea is a malformed common cavity cochlea. 